Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: Polymer Dynamics

CPP 33.5: Vortrag

Donnerstag, 29. März 2012, 10:45–11:00, C 264

Excitation Dynamics in Donor-Acceptor Copolymers — •B. Gieseking¹, B. Jäck¹, E. Preis², S. Jung², M. Forster², U. Scherf², C. Deibel¹, and V. Dyakonov^1,3 — ¹Experimental Physics VI, Julius Maximilian University of Würzburg, D-97074 Würzburg — ²Macromolecular Chemistry and Institute for Polymer Technology, Bergische University of Wuppertal, D-42097 Wuppertal — ³Bavarian Centre for Applied Energy Research (ZAE Bayern), D-97074 Würzburg

Recently the efficiency of organic bulk heterojunction solar cells could be significantly increased by using donor–acceptor type copolymers in the active device layer. Nevertheless only little is known about the elementary processes following photoexcitation of these materials.

Here we present an in-depth study of the excitation dynamics in the copolymer PCDTBT. By carrying out comparative steady state absorption and photoluminescence (PL) measurements on PCDTBT and its building blocks we assign the two prominent absorption bands to two spatially separated co-monomer units on the polymer chain coupled by an efficient energy transfer process. The relaxation dynamics investigated by time-resolved PL spectroscopy are dominated by a redshift of the spectrum while adding PC₇₀BM results in an efficient PL quenching. We find no evidence for a direct decay pathway from the higher energy band of the donor towards the acceptor. Our findings indicate that effective coupling between copolymer building blocks leading to the energy transfer between comonomer units governs the photovoltaic performance of the blends.